All uses of electricity eventually require voltage measurements. Residential and commercial wiring installations, air conditioning systems, vehicle electrical systems, computer repair, and monitoring of laboratory experiments all require voltage measurements. One type of voltage probe common in the industry is a set of two spikes, each having an insulated holding portion and a pointed end that is forced into contact with an electrical conductor by an operator gripping the insulated portion. The spikes typically conduct current through flexible insulated wire leads attached to the ends of the spikes opposite the points. The leads are attached to the measurement device, typically a meter that senses the voltage drop between the two conductors in contact with the two spike points. Of the many other available probes, some take the shape of alligator clips, L-shaped clips, or hook-shaped clips.
Because a measurement with spike probes generally requires two hands, holding or adjusting the meter or holding another tool while simultaneously making a measurement, is almost impossible, particularly where the contacts are not easily accessible. Also, alligator clips and other clip-on probes are only capable of attachment to contacts that have features small enough to be gripped by the clips. Contacts such as the heads of countersunk or round, oval, or pan-head screws, for example, are extremely difficult to grip with clip-on probes. For such contacts, hand-held spike probes are used.